A new study concludes that a quantum internet is feasible at a global scale, previewing what tomorrow’s global communications might look like.

Image in public domain.

Few words sound better together than “quantum” and “internet” — it sounds like the future, and it very possibly is the future. A group of researchers at the University of Padova, in Italy, carried out an experiment between satellites in orbit and a station on the ground. Using existing quantum technology they were able to pass a signal over some 20,000 kilometres (12,427 miles) of air and space without any significant interference or data loss, showcasing the feasibility of secure quantum communications on a global scale.

“Space quantum communications (QC) represent a promising way to guarantee unconditional security for satellite-to-ground and inter-satellite optical links, by using quantum information protocols as quantum key distribution (QKD),” says one of the researchers, Giuseppe Vallone from the University of Padova in Italy.

Essentially, the team carried out an exchange of pulse photons, using two different satellites in the Russian GLONASS constellation and the Space Geodesy Centre of the Italian Space Agency. These are global positioning satellite systems, similar to GPS. Together, all these systems are called the Global Navigation Satellite System (GNSS).

Co-lead author Professor Paolo Villoresi explains:

“Our experiment used the passive retro-reflectors mounted on the satellites. By estimating the actual losses of the channel, we can evaluate the characteristics of both a dedicated quantum payload and a receiving ground station.”

“Our results prove the feasibility of QC from GNSS in terms of achievable signal-to-noise ratio and detection rate. Our work extends the limit of long-distance free-space single-photon exchange. The longest channel length previously demonstrated was around 7,000 km, in an experiment using a Medium-Earth-Orbit (MEO) satellite that we reported in 2016.”

While the study showed that such transmissions are feasible, it’s still only a proof of concept, and it will be a long time before anything is developed practically. In a potential quantum internet, speeds will be very slow for the foreseeable future,

The lure of a potential quantum internet comes from security — essentially, quantum communications are encrypted and unbreakable. Thanks to the nature of the technology, any interference is quickly detected, making QKD communications impossible to intercept. If a message sent through quantum technology would be hacked by a third party, it would be destroyed.

So while this likely won’t make our internet faster or cooler anytime soon, it could revolutionize a number of communications, making them more reliable and safer.

“Satellite-based technologies enable a wide range of civil, scientific and military applications like communications, navigation and timing, remote sensing, meteorology, reconnaissance, search and rescue, space exploration and astronomy,” Vallone concludes.

The study “Towards quantum communication from global navigation satellite system”, by Calderaro et al, has been published in the journal Quantum Science and Technology.